Methods for formation of a video image with three monochrome cathode ray tubes (CRT) of primary colors red (R), green (G), and blue (B) are well-known, for example, a U.S. Patent Application No. 2005/0062896 filed on Mar. 24, 2005. In that method, images of primary colors (R, G, B), formed on separate CRTs, are projected on a common screen by means of projection objectives (lenses) and catadioptric optics, whereon superimposing the images occurs, and a color image is generated.
Another method, wherein images from three CRTs are preliminary combined by means of a cubic prism and dichroic (color-separating) mirrors and then projected on a common screen, is described in a Russian Federation patent No RU 2082206, as of Jun. 20, 1997. However, the following specific problems and drawbacks can be found in all known methods deploying three CRTs:
A) While projecting the three spatially separated images on the common screen, difficult-to-remove trapezoidal distortions arise.
B) Dissimilar changes of CRTs' characteristics in the course of time (due to dissimilar ageing, deterioration) result in image blur.
C) Devices that use three CRTs have large overall dimensions and mass, i.e. they are cumbersome.
D) The adjustment of the image congruence is carried out by mechanical means, which often lack precession.
The proposed invention is developed to solve the aforementioned problems, essentially differs from the currently used methods, and is aimed to significantly increase the quality of projected images.